Peer-to-peer (P2P) networks are well-known distributed computer systems which have no centralized control or hierarchical organization (see, for example, J. Li et al., “A Scalable Location Service for Geographic Ad Hoc Routing”, Proceedings ACM/IEEE Mobicom, pp. 120-130, August 2000, which is hereby incorporated by reference). Features of P2P networks which have attracted use of such systems include (1) the lack of a central server thereby making it easier for users to form a P2P network without a significant hardware investment to operate the desired network; (2) leveraging a large amount of processing and storage resources which would otherwise be idle or operated at lower efficiencies; and (3) a certain degree of robustness to faults which facilitates long term storage.
One well-known P2P architecture is the so-called “Freenet” which is a distributed information storage system (see, I. Clarke et al., “Protecting Free Expression Online with Freenet”, IEEE Internet Computing, pp. 40-49, January-February 2002, which is hereby incorporated by reference; and www.freenetproject.org). Freenet, among other things, provides a scalable and fault tolerant storage system which operates using a completely decentralized architecture and a self-organizing P2P network that pools unused disk space across large numbers of desktop computers to create a collaborative virtual file system (see, Clarke supra at p. 40). Participants in the Freenet system each run a node that provides the network a certain storage space. To add a new file, a user sends the network an insert message containing the file and its so-called location-independent globally unique identifier (GUID) which causes the file to be stored on some set of nodes (see, Clarke supra at p. 44). During a file's lifetime, it might migrate to or be replicated on other nodes, and is ultimately retrieved by a user through the broadcast of the GUID request such that when the GUID request reaches the node holding the particular file that node passes the file back to the requester. Freenet's designers focused (see, Clarke supra at p. 41) on four main features: (1) privacy; (2) resistance to information censorship; (3) high availability and reliability through decentralization; and (4) efficient, scalable and adaptive storage and routing. Freenet's decentralization, anonymity of reader/writers and encrypted content make Freenet more robust against hostile attacks. However, Freenet does not explicitly try to guarantee permanent data storage instead using a probalistic storage policy (see, Clarke supra at p. 46) which requires a node upon receiving a new file (and faced with a storage capacity problem) to delete the least recently requested files in its data store until enough storage is cleared for the newly arrived file.
In addition to Freenet, there exist several other well-known P2P file storage systems such as “OceanStore” (see, S. Rhea et al., “Maintenance-Free Global Data Storage”, IEEE Internet Computing, pp. 40-49, September-October 2001, which is hereby incorporated by reference), the “Cooperative File System” (see, F. Dabek et al., “Wide-Area Cooperative Storage with CFS”, Proc. 18th ACM Symp. Operating System Principles (SOSP 2001), ACM Press, New York, 2001, which is hereby incorporated by reference), and “PAST” (see, A. Rowstron et al., “Storage Management and Caching in PAST, a Large-Scale, Persistent Peer-to-Peer Storage Utility”, Proc. 18th ACM Symp. Operating System Principles (SOSP 2001), ACM Press, New York, 2001, which is hereby incorporated by reference). Each of these P2P networks focus more on efficient data location rather than security against malicious attacks.
The aforementioned P2P networks provide for the storage and replication of an individual's data across a geographic area and provide certain levels of protection from malicious attacks. In delivering such P2P storage attributes to their users, these types of P2P networks utilize various schemes that allow for the quick mapping from data description (e.g., file name) to the location of replicas (or directories describing the replicas). While such quick mapping works well to protect data from faulty media or disasters they remain vulnerable to direct attacks. That is, quick mapping provides faster retrievals and redundancy protects data from faulty media or other disasters. However, such fast direct access implies that disrupting a few, statically determined, systems will suffice to disrupt access. Further, there is no defense against well-known denial-of-service (DOS) attacks caused by the mere insertion (by a hacker or other person intent on doing harm) of “junk” data into the network. That is, by the time a determination is made (if ever) that the network is being subject to a DOS a large amount of data may be lost forever. Such vulnerability stems from the ease at which data or data directories can be quickly determined and attacked by unauthorized users.
In K. G. Anagnostakis et al., “Exchange-based Incentive Mechanisms for Peer-to-Peer File Sharing”, IEEE International Conference on Distributed Computing (ICDCS 2004), Tokyo, Japan, Mar. 23-26, 2004, which is hereby incorporated by reference, a peer-to-peer filing sharing system is described which employs both so-called “exchange transfers” and “non-exchange transfers” whereby users share resources between themselves. The exchange transfers in this system occur only amongst peers that choose to participate in a N-way exchange amongst a ring of N peers, where each peer is served by its predecessor and serves its successor in the ring. As such, this system employs a fixed ring of peers amongst which exchange transfers may occur. Otherwise, non-exchange transfers are possible where no sharing of resources is required.
Thus, there exists a need for an enhanced peer-to-peer technique that addresses the aforementioned vulnerabilities related to malicious attacks while maintaining an effective distributed storage solution which is free form (i.e., non-fixed) in nature to increase flexibility and transferability amongst peers thereto.